Fluoropolymers such as polytetrafluoroethylene (PTFE), polychlorotrifluoro-ethylene (PCTFE) and polyvinylidene fluoride (PVDF) are well known for having excellent thermal, chemical, and weather resistance, along with favorable properties like water and oil resistance. Unfortunately, the use of such fluoropolymers in coatings is difficult owing to their poor solubility in industrial solvents—such as xylene and butyl acetate—which are typically used in the coating industry. Instead, more exotic solvents must often be used, which not only affect the economics of a coating, but can also present environmental issues owing to, e.g., potential toxicity of the exotic solvents.
Accordingly, there is a need to formulate alternative coatings which have superior performance properties, yet can use economical industrial solvents and be environmentally friendly.
Furthermore, polymerization of fluorinated polymers presents a number of challenges, e.g., as detailed in prior application Ser. No. 13/645,437 (now U.S. Patent Publication No. 2013/0090439 A1), incorporated herein by reference. Although several types of polymerization methods to make tetrafluoropropene copolymers have been described in prior application Ser. No. 13/645,437, Applicants have come to further appreciate that these polymerization methods have undesirable aspects or limitations, and/or that the polymers produced thereby can be formed with different and/or improved properties.
Accordingly, Applicants have come to appreciate a need to develop improved processes for making tetrafluoropropene copolymers having different and/or improved properties for uses in various applications.